Skip to main content

Full text of "The Morphology And Evolution Of The Apes And Man"

See other formats


THE  MUSCULAB SYSTEM                 189
into the distal part of the phalanx in the Gibbon. The opponens minimi digiti (O.M.D.) has a double origin from the anterior annular ligament and hook of the unciform ; it is inserted into the ulnar aspect of the shaft of the fifth metacarpal bone.
Thenar Muscles (fig. 35).—The abductor pollicis brevis (A.P.B.) arises in the Orang and Gorilla from the anterior annular ligament, but it has an additional origin in the Chimpanzee from the scaphoid and sesamoid bone of the thumb. It may be divided into slips. It is inserted into the radial aspect of the base of the first phalanx of the thumb. The opponenspollicis (O.P.) arises from the anterior annular ligament and ridge on the trapezium ; and it is inserted into the distal half of the shaft of the first metacarpal in all Apes except the Gibbon, in which it sends prolongations to the pollical phalanges. The flexor brevis pollicis (F.B.P.)has superficial and deep heads in all Apes except the Gorilla. The former arises from the anterior annular ligament and trapezium ; and the latter springs from the anterior annular ligament and ulnar side of the first metacarpal bone. . It is inserted into the ulnar side of the base of the proximal phalanx of the thumb. The Gorilla differs from all other Apes and Man in possessing the deep head only.
The adductor transversus pollicis is easily separated from the oblique adductor in Man and all the Apes except the Gibbons. It arises from a septum lying along the palmar aspect of the third metacarpal, but it gets an additional slip from the second and third meta-carpals in the Gorilla. It is inserted into the ulnar aspect of the first phalanxj of the thumb in the larger Apes; but it gets an additional insertion to the ulnar